Hydraulic system for reciprocating breaker plates for reversible rotary crushers



April 27, 194s.

F. J. WRIGHT HYDRAULIC SYSTEM FOR RECIPROCATING BREAKER PLATES Foa REVERSIBLE ROTARY cnusEEns Filed July 10, 1945 2 Sheets-Sheet 1 /NVEN To@ i FRED J. We GHT,

HTT'Y Apnl 27, 1948. F. `LWRIGHT 2,440,388

HYDRAULIC SYSTEM FOR RECIPROCATING BREAKER `PLATES FOR REVERSIBLE ROTARY CRUSHERS Filed July 10, 1945 2 Sheets-Sheet 2 n3 s m M T. i

/\\ Mgg* Patented Apr. 27, 1948 HYDRAULIC SYSTEM` FOR RECIPROCATING BREAKER PLATES FOR REVERSIBLE R- TARY CRUSHERS Fred' J. wright, Upper Arlington, by mesnov assignments, to The Ohio, assignor, Jeil'rey Manufacturing Company, a corporation of Ohio AppiicatlonJuiy 10, 1945, Serial No.'604,219

Claims. (Cl. 241-187) This invention relates to a hydraulic system and particularly to such a system, per se, and in combination with a reversible reciprocating breaker plate type of crusher.

An objectl of the invention therefore is to provide an improved hydraulic system which is particularly useful in connection with a crusher of the above mentioned type but which, in its broad er aspects, may have other uses.

A further object of the invention is to provide a crusher with hydraulic apparatus for adjusting similar reciprocating breaker plates so that the breaker plates counterbalance each other and reciprocate oppositely simultaneously.

A furtherA object of the invention is to provide a crusher or other machine with a hydraulic system in which there are two reciprocating breaker plates or members operated by hydraulic motorsthere being valve means provided to insure a predetermined travel of each breaker plate or member independently of the travel of the other one.

Other objects of the invention will appear hereinafter, the novel features and combinations being set forth.in the appended claims.

In the accompanying drawings,

Fig. 1 is a sectional elevational view of a crusher incorporating reciprocating breaker plates which are controlled by the hydraulic system of my invention and which in combination therewith constitutes one aspect of the invention;

Fig. 2 is a piping diagram of the hydraulic system of my invention;

Fig. 3 is a sectional view of one of the control valves for starting and stopping the system;

Fig. 4 is a sectional view of a speed or hydraulic fluid volume contro1 valve; y

Fig. 5 is a sectional view of one of the controlV valves;

Fig. 6-is a view of the valve of Fig. 5, taken at right angles to the view of Fig. 5, vwith the lower portion shown in section;

Fig. 7 is a sectional view ofV another control valve:

Fig. 8 is a sectional view of a uid pressure actuated four-way valve employed in the system; and

Fig. 9 is a sectional view of another fluid pressure actuated four-way valve employed in the system. f

Referring rst to Fig. 1 of the drawings, there is illustrated a'crusher which incorporates structure disclosed in full detail in the application of Lloyd K. Knight, Serial No. 603,367, led July 5, 1945, entitled Crusher.

Briefly described, the crusher includes a main frame III which is built up oi a plurality of parts housing for the principal working parts of the crusher. Said main frame i0 includes a generally rectangular base I I upon which is mounted a pair c1' side frame members I2 each formed hva pluralitj' of attached plates or segments.

As best seen in Fig". 1 oi the drawings, the main frame Ill-provides a reducing chamber I3 within which reduction of the material takes place. The side walls of reducing chamber I3 are provided with removable wear platesV i4 which are carried principally by the side frame members I2, some of the bottom Wear plates I4, however, being carried by the base l I.

Mounted for rotation within the reducing chamber I3 is a rotor I5 which is shown -as of the swing hammer type, being provided with a plurality of swing hammers I6. Rotor I5 includes a rotor shaft II, the opposite ends of which are mounted on appropriate bearings carried 'in bearing boxes, said bearing boxes being mounted on pedestals provided by the base II. On one end the shaft I'I carries a pulley or ilexible coupling by which the rotor I5 may be rotated in reverse directions as desired.

Since the crusher is designed for selective reverse rotation, thus materially increasing its life without requiring the renewal oi' parts. it is generally symmetrical.

Adjacent the bottom portion of the reducing chamber I3 there is a pair ci spaced screens I 9,

the bottom bars of which'may be spaced apart to provide a free opening for the material to pass through and through the bottom of the open base I I. Adjacent the upper edge of each screen I9 I provide a pair oi' transversely-extending breaker bars 20 which are mounted for adjustment toward and from the axis of the rotor I5 by adjusting means adjacent the opposite ends of each bar 20.

Positioned on top breaker bar 20 is a scraper 22, the upper edge of which denes the bottom limit or boundary of an exposed area at which an upwardly and inwardly extending traveling 0r reciprocable breaker plate 23 is provided and Y' As a consequence, by reciprocating the traveling f breaker plates 23, the wear plates 28, or, in other words. the wearing surfaces or areas of said breaker plates 23, are successively exposed or brought into operative position.

The breaker plates 23 are mounted for traveling or reciprocatory motion in guide means provided by the main frame ill so that they may reciprocate between the two positions illustrated or indicated in Fig. 1 of the drawings, successively exposing the upper and lower Wearplates 26. -This reciprocatory motion is provided by a pair of hydraulic piston motors or Jacks 21, one for each Y of the breaker plates 23. The piston motors 21 are carried in compartments provided by the main frame l0 behind the breaker plates 23 and the outer ends of their piston rods are connected by a. loose or flexible connecting means 23 with the upper ends of the breaker plates 23.

'I'he piston motors 21 are preferably interconnected so that there is a counterbalanclng effect between the two breaker plates 23 in that one of them moves downwardly while the lother moves upwardly. The apparatus or system for accomplishing this result is disclosed in full detail hereinafter.

Material to be crushed, such as iron ore. is fed to the feed chamber I3 by a pivoted or swingable feed chute 29 which is disclosed in full detail and claimed in the above mentioned application of Lloyd K. Knight. Feed chute 23 in turn is fed by a stationary feed pipe or chute 30 which is removably attached to the main frame I0.

Attention is now directed particularlyto Figs. 2 to 8, inclusive, of the drawings. andato the hydraulic system which provides for reciprocation of the two motors 21 and through them the two breaker plates 23. The hydraulic system includes a motor driven pump 3| which derives hydraulic fluid from a tank 32 and delivers it by way of a pipe or conduit 33 to a combination volume control and high pressure relief valve 3|, the interior details of which are shown in Fig. 4 of the drawings. This valve may be a standard valve having the above mentioned characteristics.

'I'he mode of operation of such a valve is well known in the hydraulic art and, briefly described, is as follows. Fluid delivered to it through feed pipe or conduit 33 ilows through a variable oriilce 35 and out to the system by way of pipe or conduit 35. v The volume which yis delivered to the pipe 36 is determined by the size of the orifice 35 which may be varied by rotation of a shaft 31 upon which oriiice 35 is formed. 'Ihe hydraulic fluid delivered by the pipe or conduit 33 is received in a chamber 33 before ilowlng lthrough the orice 35 and a by-pass controlling piston 33 is reciprocably mounted in a cylinder communicating with the chamber 33.

A passageway Il is formed in the body of the valve 34 and communicates hydraulic iluid under pressure on the output side `of orifice 35 to the opposite side of the piston 33 from that communicating with and subject to the pressure in chamber 33. A coil spring l2 illses a W'PBSS valve 43, attached to piston 33, to by-pass closing position. A by-pass or drain pipe or conduit M which is .controlled by the valve 43 leads from the chamber 38 to tank 32.

For any given size oriilce 35 the piston 33 will operate atuomatically, as determined by the pressure drop caused by the iiow of hydraulic uid through said orifice 35, to by-pass the excess oil delivered by the pump 3| to the pipe M.

Also in communication with the passageway l0 is an adjustable high pressure relief valve 45 and this relief valve, of course, determines the maximum pressure which can appear in the feed pipe or conduit 33. In case this pressure is sutilcient to open relief valve I5, the high pressure fluid is free to drain by passageway I3 into conduit 44 which, as above mentioned, leads to the tank 32.

Also communicating with said passageway 46 is a conduit or pipe 41 which leads to a start and stop valve 48 shown in detail in Fig. 3 of the drawings. This start and stop valve is a very simple spool type valve including a casing 43 having a cylindrical bore 50 in which there is a spool 5i having a pair of spaced lands 52 and 53. Spool 5I is provided with an actuating rod and handle 54. Pipe 41 leads to the bore 50, and a pipe or conduit 55 leads therefrom to tank 32.

When the spool 5| is in the position illustrated lin Fig. 3, the system will be in operation because the drain pipe 41 will be sealed by the land 52. To stop the system the spool 5I s'moved to the left, as viewed in Fig. 3, whereupon conduit 41 is connected to tank 32 by way of conduit 55, the two conduits being in communication by virtue oi the reduced portion of spool 5| between lands 52 and 53. pressure will be developed in the hydraulic system since the output of the pump 3| will be eiifectively lay-passed and consequently there will be no hydraulic iluid under pressure available to 0perate the piston motors 21.

Under operating conditions, hydraulic fluid will be delivered, as above mentioned, at any one oi' a plurality of preselected volumes and at a maximum variable predetermined pressure to conduit 33 which includes a check valve 55 operating to prevent reverse ilow o1' hydraulic fluid to the pump 3l. thus prohibiting the possibility of regeneration which might cause damage. After passing through check valve 55, the hydraulic fluid is delivered to a pressure sequence valve 51 which is disclosed in detail in Figs. 5 and 6 of the drawings.

The function and structure of the valve 51 will be described more completely hereinafter. For the time being it is suillcient to say that under most conditions the hydraulic iluid simply ilows through this valve, the inlet and outlet portions of which are connected by virtue ot a central chamber 53 formed in a body 53 thereof. From the valve 51 the conduit 36 branches into two .pipes or conduits 53 and 5|. Conduit 6l leads to a main four-way reversing valve 62, and conduit 5| leads to a control four-way valve 53 which,

as hereinafter described. controls the reversing movement of the four-way valve l2. The construction of valve 52 is shown in detail in Fig. 8 of the drawings, and valve 33 is of substantially identicalconstruction. asshown ln Fig. 9.

Valve 32 includes a body 64 provided with a central cylindrical bore 5l within which there is a spool 33 provided with 'three spaced lands 51, 63 and 33. Communicating with the bore 55 are live successive chambers. the center one or which com- Under such conditions, substantially no munic'ates with conduit 80, the nexttwo of which on opposite [sides of the center oney communicate with cylinder or motor pipes or conduits 18 and 1|, respectively, and the two end .chambers are connected in parallel and both connected to a drain or tank pipe or conduit 12 which leads back to the tank 32. t

It is obvious from Fig. 8 of the drawings that hydraulic fluid under pressure delivered to the pipe or conduit 80 may be delivered selectively to the pipes 10 and 1|: the other of said pipes 10 and 1I being connected to tank or drain. Consequently, by shifting the spool 88, the direction of flow of hydraulic fluid through pipes 18 and 1I may be reversed and, as hereinafter described, the spool 66 is shifted to eil'ect reversal or reciprocation of the two motors 21 which are connected in series and which are preferably operated in reverse directions: that is, one of them isexpanding while the other is contracting and consequently one of the breaker plates 23 is moving upwardly while the other is moving downwardly and vice versa.

Pipe 10 leads to the piston rod end of the righthand hydraulic pistonl motor 21, as viewed in Figs. l and 2, through a control valve 13 which is shown in some detail in Fig, 7 of the drawings. 'I'he pipe 1| leads to the piston rod end oi the left-hand hydraulic piston motor 21, as viewed in Figs. 1 and 2, through a control valve 14 which is similar to control valve 1-3. The structure of these valves 13 and 14 is described in detail hereinafter, but, for the time being, it is Isufficient to note that under most operating conditions the hydraulic fluid merely flows through a central chamber 15 formed in a body 16 thereof.

The piston motors 21 are of the double acting type and the head ends are connected together by pipe or conduit 11 which leads to a pressure sequence valve 18 which is similar in construction to the valve 51.

Hydraulic fluid which is delivered to the conduit 60, as above described, will ow through the reversing valve 62', when the spool 66 is in the position illustrated in Fig. 8, and be delivered to the conduit 1 i, flowing through it and through the valve 14 to the piston rod end of the left-hand hydraulic piston motor 21. This hydraulic fluid entering the cylinder of said motor 21 will cause the piston and piston rod to move downwardly and thus cause the associated left-hand breaker plate 23 of the crusher to move downwardly. The downwardly moving piston will force oil or hydraulic fluid from the bottom of the cylinder to the conduit 11 and into the bottom of the cylinder of the right-hand piston motor 21. This, of course, will move the piston of right-hand cylinder upwardly and the hydraulic fluid on the piston rod side of the piston will ilow through conduit 18 an-d valve 13 back through the four-way valve 62 and to the tank or drain pipe 12 with which it is in communication. This flow of hydraulic fluid"will, of course, produce downward movement of the left-hand piston 21 and the lefthand breaker plate 23 and upward movement of the right-hand piston 21 and the right-hand breaker plate 23.

It is to be particularly noted that the portion of the conduit 11 which interconnects the two piston motors 21 provides a hydraulic coupling so that the Weight of each breaker plateA 23 or other mechanisms supported by thepiston motors 21 counterbalances each other. Obviously, if these breaker plates or other mechanisms are not of the same weight the counterbalancing effect will not 6 be complete, but in the particular machine herein disclosed the counterbalance will be substantially complete as the two breaker plates 23 are substantially identical. 4

This counterbalanclng feature is an important contribution of my invention as it reduces maly blocked, as hereinafter described, and has no immediate function.

When .the left-hand piston motor 21 reaches the end of its stroke it is obvious that pressure will be built up in the pipe or conduit 1i and this pressure is employed tocontrol the valves 14 and B3 so as to reverse the four-way valve 82 by moving the spool '86 in the opposite direction from that illustrated in Fig. 8. When such a, condition is realized, it isv obvious that hydraulic fluid delivered to the conduit 88 will be directed to conduit 10, and conduit 1I will be connected to tank, thus producing a reverse travel of the two piston motors 21 from that previouslydescribed. This reverse travel will continue until right-hand motor 21 reaches the end of its stroke, whereupon 'valve 13 will control valve 82 again to reverse the spool 6,6 of valve 62. The manner in which these reversals take place is as follows.

Assuming right-hand piston motor 21 has reached the end of its stroke, pressure will immediately build up in the pipe 18 and this will actuate valve 13. In order to understand the operation of valve 13 it is necessary first to understand the operation of valve 51 since it is similar thereto, except' for two differences which will be pointed out. The body 59 of valve 51 has an upright cylindrical bore 18 which extends through the previously mentioned central chamber 58. A spool recipiocates in the bore 19 and is provided with upper and lower lands 8| and 82. An adjustable spring 83 provides downward pressure on the top of the spool 80 and adjustment of its compression determines the pressure at which this valve opens.

In a removable base 84 of valve 51 there is a small piston 85, reciprocable in a bore, the bottom of which communicates with the chamber 58 by way of passageway 8B. Thus the pressure of the hydraulic fluid in the chamber 58 is communicated to push upwardly on the piston 85 and in The chamber 81 is connected to the pipe orconduit 11 leading between the valve 51 andthe valve 18. In other words, conduit 11 has the valve 18 connected between input and output branches thereof in a manner similar to that in which valve 51 is connected between branches of conduit or pipe 36. Stated another way and in accordance with a previous suggestion, that portion of conduit 11 between the right-hand motor 21 and the valve 51.has valve 418 connected therein and the passageway of conduit 11 is normally unobstructed by the valve 18. However, .with the spool of valve 51 in the position illustrated in Figs. 5 and 6, conduit 11 is blocked by the spool 80 thereof and consequently the hydraulic uid which is 7 forced from the left-hand piston motor 21, as it is forced down to the right-hand piston motor 21. cannot be by-passed through the branch of pipe 11 leading through the valve 18 tothe valve 51.

Any leakage of'hydraulic fluid past the land 8| to the area above it will be drained into chamber 81.

As previously mentioned, the valve 13 is substantially the same construction as valve 51, `except for two added features. That isl valve 13 has a spool 88 with top and bottom lands, the spool being urged downwardly b'y an adjustable spring 89 and being urged upwardly by a small piston 90 which is urged upwardly by hydraulic fluid delivered thereto through a bore. not shown, communicating with the central chamber 15. Whenever the pressure in the chamber 15 reaches a predetermined value, suillcient to move the spool 88 upwardly, chamber 15 will communicate with an upper chamber 9| and deliver hydraulic fluid to a conduit or pipe 92 which is connected to the left-hand end of the four-way valve 63. Whenever this valve 13 is thus actuated and fluid is delivered to the left-hand end of four-Way valve 63, it will have its spool moved to the right.

Under such conditions the hydraulic fluid delivered to the branch or conduit 8| is directed by the four-way valve 63 to a pipe or conduit 93 which communicates with the left-hand end of the bore 65 of four-Way valve 62 and thus actu- 13 is that the latter is provided with a drain or tank pipe or conduit 98 for draining oil which accumulates above the upper land of spool 88. Valve 14 is similarly connected with drain pipe 12. i

From the above description it, is obvious that the sequence valves 13 and 14 control the spool of four-way valve 63 which in turn controls by volume control valve 34, the speed or rate ates the spool 6B thereof to the right. as viewed in Fig. 8 of the drawings.

Also under such conditions the lhydraulic fluid under pressure is diverted from pipe 10 to the pipe 1| and the piston motors 21 are actuated in their reverse directions, with the left-hand one moving downwardly or contracting and the right-hand one moving upwardly or expanding. This will continue until the piston of the lefthand motor 21 reaches the end of its stroke, whereupon pressure will build up in valve 14 and hydraulic fluid under pressure will be bypassed by said valve 14 to a pipe or conduit 94 and delivered to the right-hand-end of four-way valve 63, shifting its spool and directing the hydraulic fluid under pressure from the conduit 6| to a. conduit similar to 93 which leads to the right-hand end of the four-way valve 62 and will move the spool 66 thereof to the left.

As above mentioned, the valves 13 and 14 are of similar construction and thus the operation of each of them will be understood` from the above description of valve 13.

The two differences between the valves 13 and 14' on the one hand and the valves 51 and 18 on the other hand are evident from a consideration of valve 13 as compared with valve 51. Said valve 13 has a built-in check valve 95 which permits a flow of fluid from chamber 9| to chamber 15, but not in the other direction. The function of this is to provide for release of hydraulic fluid in the bore of four-way valve 83 whenever its spool i8 is shifted. since hydraulic fluid forcing it in one direction will require fluid ou the other end of the spool to be released. For example, if the spool ofvalve 83 is moved to the left, as viewed in Fig. 2, fluid will be free to flow through the pipe or conduit 92 to the chamber 8| and by check valve 95 to chamber 19 which is connected to pipe 10 which,

der such conditions. is connected by four-way valve 82 to drain through pipe 12. Reverse movement of the spool of valve 83 is similarly aceommodatedbyvalve 14.

of reciprocation of the motors 21 may be variably determined at any one of a plurality of different values. Furthermore, the valve 34 provides a. high pressure relief, thus protecting the hydraulic system. The start and stop valve 48 provides for starting and stopping of the reciprocating apparatus.

The function of the valve 51 is to insure that if one of the motors 21 reaches the end of its stroke before the other one does when they are traveling in one direction, the second motor will complete its stroke, and the function of the valve 18 is similar except for the other motor.

Valve 51 operates as follows. It is set to open at a relatively low pressure. For example, it may be set at a pressure of fifty to one hundred pounds per square inch, where the relief valve 45 is set, for example, at approximately nine hundred pounds per square inch. Assuming that hydraulic fluid under pressure is being delivered to the pipe 1| and left-hand motor 21 reaches the end of its stroke before right-hand motor 21 has reached the end of its stroke; as above described, when left-hand motor4 21 reaches the end of its stroke, pressure is developed in the line 1|, which ultimately actuates valve 14.

Valves 13 and 14 are preferably set to open at about eight hundred pounds per square inch in the system described, it being understood that in all cases where pressures are given they are merely relative and illustrative of one working arrangement. Valve 51, however, operates at very low pressure; for example, from fifty to one hundred pounds, and consequently it will open before valve 14 opens. By virtue of its opening,

` hydraulic fluid flowing through a by-pass circuit provided by pipe 38 in chamber 58 will be free to flow through pipe 11 and valve 18, reaching the lower end' of the cylinder of right-hand piston motor 21 and causing this piston motor to complete its travel before it is possible for the pressure in line 1| to build up to a high value to operate valve 14. In other words, valve 14 can only be operated in case left-hand piston motor 21 has reached its complete downward stroke, and right-hand piston motor 21 has reached its complete upward stroke.

If, during the movement above described, the right-hand motor 21 reached the upward end of its stroke before the left-hand motor 21 reached the end 'of its stroke, compensation takes place as follows. to the end that left-hand motor 21 may complete its stroke. Right-hand motor 21 having completed its stroke, it is no 'longer possible to feed hydraulic fluid from left-hand motor 21 to right-hand motor 21. Therefore-t0 coml The second difference between valves 51 and 76 .plete the stroke of left-handv motor 21, the retank or maining fluid in it must be drained to tank. This is effected by the iluid ilowing over a by-pass circuit including pipe 11 leading into valve 18. Valve 18 is set to open at a pressure of, for example, seven hundred and fty pounds per square inch, or slightly below the pressure at which valves 13 and 14 open, which may be, for example, eight hundred pounds per square inch. Therefore, as the pressure builds up in pipe 1I which is communicated through left-hand motor 21 to pipe 11, the pressure in valve 18 will build up to a. predetermined value which, in the illustration given, was seven hundred and ifty pounds, whereupon said valve will open and connect pipe 11 by way of a pipe or conduit 91 to drain or tank conduit 96.

Valve 18 will, of course, stay open until lefthand motor 21 completes its travel, whereuponl the pressure in the system and particularly in pipe 1| will increase to actuate valve 14 which, as previously described, will reverse the fluid flow to the motors 21, reversing their operation.

It may be stated that the valves 51 and 18 operate to insure complete travel of the two motors 21 in each of their extreme positions in a manner which will be obvious from the above description.

Therefore, in the operation of the crusher the breaker plates 23 or reciprocating members which are reciprocated by the double acting hydraulic piston motors 21, are interconnected by a fluid coupling so that they are normally in balance,

moving in a teeter-totter fashion, with one traveling upward while the other travels downward, and vice versa. Their rate of reciprocation can be adjusted over a wide range by adjusting the valve 34. Furthermore, the system not only provides for automatic reversal of each piston motor or breaker plate, but also provides for their synchronization, or, in other words, insures that each shall make a complete travel through a predetermined distance.

Itmay be further stated that the valves 3l. 62,4 63, 13, 14, 51 and 18 are all standard valves, but insofar as applicant is aware the particular system herein disclosed and claimed has not heretofore been produced.

`Obviously those skilled in the art may make various changes in the details and arrangement of parts without departing from the spirit and scope of the invention as dened by the claims hereto appended, and I therefore wish not to be restricted to the precise construction herein disclosed. Y

Having thus shown and described an embodiment of my invention, what I desire to secure by Letters Patent of the United States is:

1. A lcrusher including a rotor, a pair of reciprocably mounted breaker plates adjacent said rotor; hydraulic motor means for reciprocating said breaker plates in reverse directions simultaneously upwardly and downwardly. a hydraulic circuit for controlling reciprocation ot said breaker plates including a reversible hydraulic motor for each plate, a hydraulic circuit for controlling said motors including means providing a hydraulic coupling between them whereby the weight of each breaker plate counterbalances the other and said breaker plates are moved in reverse directions as aforesaid, and valve means operable to reverse the direction oi travel of said motors periodically and insure that each breaker plate moves through a full stroke.

3. -A crusher including a rotor. a pair of reciprocably mounted breaker plates adjacent said rotor, hydraulic motor means for reciprocating said breaker plates in reverse directions simultaneously upwardly and downwardly, a hydraulic circuit for controlling reciprocation of said breaker plates including a reversible hydraulic motor for each plate, a 'hydraulic circuit Vfor controlling said motors including means providing a hydraulic coupling between them whereby the weight of each breaker plate counterbalances the other and said breaker plates are moved in reverse directions as aforesaid, and valve means operable to reverse the direction of travel of said motors periodically.

3. A crusher including a rotor, a pair of reciprocably mounted breaker plates adjacent said rotor, hydraulic motor means for reciprocating said breaker plates in reverse directions simultaneously upwardly and downwardly, a hydraulic circuit for controlling reciprocation of said breaker plates including a reversible hydraulic motor for each plate, and a `hydraulic circuit for controlling said motors including means providing a hydraulic.coupling between them whereby the weight of each breaker plate counterbalances the other and said breaker plates are moved in reverse directions as aforesaid.

4. A crusher including a rotor, a pair of reciprocating members adjacent said rotor, a reciprocating double-acting hydraulic piston motor for operating each member, a hydraulic circuit for controlling said motors including piping connecting them in series, pumping means for supplying iluid to said motors, and pressure responsive means in said circuit operable to cause reciprocation of said motors and to insure that each motor travels a predetermined distance including a by-pass circuit having a low pressure responsive valve operable to connect said pumping means to similar ends of said motors and a high pressure responsive valve operable to drain said by-pass circuit.

5. A machine including a pair of reciprocating members, a reciprocating double-acting hydraulic piston motor for operating each member, a hydraulic circuit for controlling said motors including piping connecting them in series, pumping means for supplying fluid to said motors, and pressure responsive means in said circuit operable to cause reciprocation of said motors and to insure-that each motor travels a predetermined distance including a by-pass circuit having a low pressure responsive valve operable to connect said pumping means to similar ends of said motors and a high pressure responsive valve operable to drain said by-pass circuit.

FRED J. WRIGHT.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date l Great Britain Jen. 17, 1938 Number Number 

